1 Scope
This part of GB/T 228 specifies the terms and definitions, symbols and designations, test piece and determination of its size, apparatus, test conditions, determination of the properties, rounding off for numerical values of test results and test report of tensile testing methods for metallic materials at low temperature.
This part is applicable to the determination of tensile properties of metallic materials at temperatures between -196 °C and <10 °C.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 228.1-2010 Metallic Materials — Tensile Testing — Part 1: Method of Test at Room Temperature (ISO 6892-1:2009, MOD)
GB/T 12160 Calibration of Extensometer Systems Used in Uniaxial Testing (GB/T 12160-2002, ISO 9513:1999, IDT)
GB/T 16825.1 Verification of Static Uniaxial Testing Machines — Part 1: Tension/Compression Testing Machines — Verification and Calibration of the Force-measuring System (GB/T 16825.1-2008, ISO 7500-1: 2004, IDT)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 228.1-2010 and the following apply.
In general, all test piece geometries/dimensions are based on measurements taken at room temperature. The exception can be the extensometer gauge length (see 3.3).
Note: The following properties are generally not determined at low temperature unless required by relevant specifications or agreement:
— permanent set strength (Rr);
— percentage permanent elongation;
— percentage permanent extension;
— percentage yield point extension (Ae);
— percentage total extension at maximum force (Agt);
— percentage plastic extension at maximum force (Ag);
— percentage total extension at fracture (At).
3.1
original gauge length
Lo
gauge length measured at room temperature before cooling of the test piece and before application of force
3.2
percentage elongation after fracture
A
permanent elongation of the gauge length, measured at room temperature, after fracture (Lu - Lo), expressed as a percentage of the original gauge length (Lo)
Note: For further details, see GB/T 228.1-2010, 3.4.2.
3.3
extensometer gauge length
Le
initial extensometer gauge length used for measurement of extension by means of an extensometer
3.4
extension
increase in the extensometer gauge length (Le) at a given moment during the test
3.4.1
percentage extension
extension expressed as a percentage of the extensometer gauge length (Le)
3.5
percentage reduction of area
Z
maximum change in cross-sectional area which has occurred during the test (So - Su), expressed as a percentage of the original cross-sectional area (So), where So and Su are calculated from the dimensions at room temperature
3.6
stress
R
force at any moment during the test divided by the original cross-sectional area (So) of the test piece
Note: All stresses referenced in this part are engineering stresses, calculated using the cross-sectional area of the test piece derived from dimensions measured at room temperature.
3.7
soaking time
ts
time taken to stabilize the temperature of the test piece prior to mechanical loading
4 Symbols and Designations
For the purposes of this part, symbols and their designations given in GB/T 228.1-2010 and Table 1 apply.

Foreword II
Introduction V
1 Scope
2 Normative References
3 Terms and Definitions
4 Symbols and Designations
5 Principle
6 Test Piece
7 Determination of Original Cross-sectional Area (So)
8 Marking the Original Gauge Length (Lo)
9 Apparatus
10 Test Conditions
11 Determination of the Tensile Properties
12 Rounding Off for Numerical Values of Test Results
13 Test Report
14 Measurement Uncertainty
15 Figures
16 Annexes
Annex A (Informative) Addition to GB/T 228.1-2010, Annexes B and D
Annex B (Informative) Example for Cooling Curves of Steel Depending on Test Piece Dimensions and the Specified Test Temperature in Ethanol and Liquid Nitrogen
Annex C (Informative) Measurement Uncertainty
Bibliography

1 Scope
This part of GB/T 228 specifies the terms and definitions, symbols and designations, test piece and determination of its size, apparatus, test conditions, determination of the properties, rounding off for numerical values of test results and test report of tensile testing methods for metallic materials at low temperature.
This part is applicable to the determination of tensile properties of metallic materials at temperatures between -196 °C and <10 °C.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 228.1-2010 Metallic Materials — Tensile Testing — Part 1: Method of Test at Room Temperature (ISO 6892-1:2009, MOD)
GB/T 12160 Calibration of Extensometer Systems Used in Uniaxial Testing (GB/T 12160-2002, ISO 9513:1999, IDT)
GB/T 16825.1 Verification of Static Uniaxial Testing Machines — Part 1: Tension/Compression Testing Machines — Verification and Calibration of the Force-measuring System (GB/T 16825.1-2008, ISO 7500-1: 2004, IDT)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 228.1-2010 and the following apply.
In general, all test piece geometries/dimensions are based on measurements taken at room temperature. The exception can be the extensometer gauge length (see 3.3).
Note: The following properties are generally not determined at low temperature unless required by relevant specifications or agreement:
— permanent set strength (Rr);
— percentage permanent elongation;
— percentage permanent extension;
— percentage yield point extension (Ae);
— percentage total extension at maximum force (Agt);
— percentage plastic extension at maximum force (Ag);
— percentage total extension at fracture (At).
3.1
original gauge length
Lo
gauge length measured at room temperature before cooling of the test piece and before application of force
3.2
percentage elongation after fracture
A
permanent elongation of the gauge length, measured at room temperature, after fracture (Lu - Lo), expressed as a percentage of the original gauge length (Lo)
Note: For further details, see GB/T 228.1-2010, 3.4.2.
3.3
extensometer gauge length
Le
initial extensometer gauge length used for measurement of extension by means of an extensometer
3.4
extension
increase in the extensometer gauge length (Le) at a given moment during the test
3.4.1
percentage extension
extension expressed as a percentage of the extensometer gauge length (Le)
3.5
percentage reduction of area
Z
maximum change in cross-sectional area which has occurred during the test (So - Su), expressed as a percentage of the original cross-sectional area (So), where So and Su are calculated from the dimensions at room temperature
3.6
stress
R
force at any moment during the test divided by the original cross-sectional area (So) of the test piece
Note: All stresses referenced in this part are engineering stresses, calculated using the cross-sectional area of the test piece derived from dimensions measured at room temperature.
3.7
soaking time
ts
time taken to stabilize the temperature of the test piece prior to mechanical loading
4 Symbols and Designations
For the purposes of this part, symbols and their designations given in GB/T 228.1-2010 and Table 1 apply.

Contents of GB/T 228.3-2019

Foreword II
Introduction V
1 Scope
2 Normative References
3 Terms and Definitions
4 Symbols and Designations
5 Principle
6 Test Piece
7 Determination of Original Cross-sectional Area (So)
8 Marking the Original Gauge Length (Lo)
9 Apparatus
10 Test Conditions
11 Determination of the Tensile Properties
12 Rounding Off for Numerical Values of Test Results
13 Test Report
14 Measurement Uncertainty
15 Figures
16 Annexes
Annex A (Informative) Addition to GB/T 228.1-2010, Annexes B and D
Annex B (Informative) Example for Cooling Curves of Steel Depending on Test Piece Dimensions and the Specified Test Temperature in Ethanol and Liquid Nitrogen
Annex C (Informative) Measurement Uncertainty
Bibliography